Pressure tank door



April 21, 1936.

R. A. DAVIS ET AL PRESSURE'TANK DOOR Filed May 17, 1954 2 Sheets-She'et vl RA. DAVIS r AL 2,037,707

PRESSURE TANK DOOR Filed May 17, 1934 2 sheetssheet 2 Patented Apr. 21, 1936- PRESSURE, TANK noon Robert A. bavis and John F. Mummert, Birmingham, Ala., assignors to Chicago Bridge & Iron Company, a corporation of Illinois Application May 17, 1934, Serial No. 726,170

' Claims. (or 220-55) This invention relates to pressure tank doors, and more particularly to doors for welded pressure vessels used in the preservation treatment of I wood, certain rubber processes, and for other 5 similar purposes.

One feature of this invention is that it provides a door capable of withstanding the high pressures developed in a tank of this type; another feature of this invention is that it permits the head plate of the door to be a spherical section, rather than'an ellipsoidal or quasi-ellipsoidal head with a short radius of vcurvature at the junction point with the shell; still another feature of this invention is that it employs rings atthe junction of the door and the shell; yet

another feature of this invention is that it permits a door .to be so designed that there is no rotational moment about the cross-sectional center of gravity of the door-ring when pressure is applied; still other features'and advantages of this invention will appear more fully from the following specification and the drawings, in which'- Figure 1 is a vertical elevation, partly in, sec-- tion, of the door; Figure 2 is a detailed sectional view along line 2-2 of Figure 1; Figure 3 is a horizontal sectional view; along the line 3-3 of Figure 1; and Figure 4 is a top detail elevation of a section of the head.

80 In the particular embodiment of this invention. illustrated herewith, the door head-plate is iii- Y dicated by the reference numeral it. This headplate is welded at the point i l to the door-ring l2. The door-ring I2 is provided with lugs l3 adapted 35 to receive between them the shank of a bolt l4; and also adapted to provide a surface against which the nut 45 and washer l6 maybe tightened.

The tank shell I! has welded thereto at the point I! a head ring l9. This head ring is provided at its outer extremity with a groove 20 in which is placed a gasket 2| against which the door-ring l2 presses when thedoor is closed. The headring l9 has bolt members 23 adapted to receive the heads 24 of the bolts l4. 45 The door ring l2 has attached thereto hingemembers 25 which pivot about hinge-pins 26, which pins are fastened to the head ring 19 by members 21. In order to open the door it is only necessary to loosen the nuts l5, swing back the 50 bolts l4 out of engagement with the lugs l3, and the door may then be swung open, its weight being carried by the hinges 25.

Inasmuch as these tanks are designed for relatively high pressure, the two rings would under- 55 go considerable strain from the various forces developed. The head ring is made considerably larger in cross-sectional area than the door-ring, and is thus capable of withstanding the various forces applie to it with little or no alteration in shape. The\door ring, on the other hand, is 5 subject to horizontal forces comprising the tension of the bolt I4 as applied to the lugs iii, the reactance of the gasket 2! as the bolt is drawn up, and the horizontal component of the tension in the head-plate in. moments about its center of gravity caused by the tension in the bolt, the vertical component of the tension in the head-plate, and the 'pres-, sure of the liquid medium within the tank as developed on the area between the joint H and 15 the point where the door ring contacts the gasket 21.

It has been found that the location of the joint I l is a very important feature in the neutralizing of the various moments developed; The tension 20 in the head-plate acts along a line which is a tangent to the spherical radius of curvature of the head-plate at the point of contact with the door ring l2, which tension is a function .of the pressure and of that radius. .The pressure per 25 inch of radius of the door-ring I2 against the gasket 2| should be about 7 times the pressure per square inch developed in the tank in order to provide a good seal. The direction of the axis of the-boltis very nearly parallel with that of the horizontal axis of the door ring, and for all practical purposes may be consideredas parallel. It is thus seen .that the tension in the bolt must equal the sum of the two outward forces consisting of the reaction of the gasket 2| and of the horizontal component of the tension in the headplate lll.

Considering the moments tending to rotate the ring about its' cross-sectional center of gravity,

it is seen that for best results the tension in the 40 bolt times the distance between the axis of the bolt and the center of gravity of the door ring, minus the vertical component of the tension in the headplate I lltimes the horizontal distance of the joint;

- II. from the center of gravity of the door ring I2, minus the pressure exertedby the liquid medium against the inner face 28 of the door ring timesthe horizontal distance between the center of pressure of said area and the center of gravity of the door ring, must equal zero for best resuits. By setting up and solving the usual me- I chanical design equations, it is found that the I proper distance between the joint II and the center of gravity of the door ring I2 is a function of the spherical main of the head-plate,

It is also subject to rotational 10' the circular radius of the ring, the length of the door ring section l2 and the height of the lugs I 3, and is independent of the pressure for any good design. Roughly, the horizontal distance Y between the joint II, or to be more exact the center of tension of the head at the point where it intersects the vertical plane through the center of gravity, and the center of gravity or the door ring l2 may be found by the following formula:

where e is the vertical distance between the axis of the bolt and the center of gravity of the door ring, R is the spherical radius of the head-plate, and r is the radius of the door ring, all three being in inches, The constant,-14 in this case, will always be double the coeiiicient of gasket pressure to gas pressure.

The above equation is derived from an equation of moments about the center of gravity of the door ring, expressed in the following equation, assuming that is the angle between the headplate at its junction with the door ring and a diameter at that point; that B is the tension in bolts, in pounds per inch of ring circumference, when pressure P in pounds per square inch exists in the tank; that his the distance from the center of gravity of the door ring to the end thereof in contact with the gasket; that y is the distance from the centerof gravity to the joint II and that the angle between the axis of the bolt and that of the door ring is sufliciently small that its cosine may be taken as unity:

Be- PRy cos 0:0

Substituting for B and for cos 0, and solving for 1, we have:'

cos 0= 1 sine 0= This equation may be written in more general form by replacing the figure 7 by the letter K, representing the desired coefiicient of gasket pressure to the pressure existing within the tank, whence:

The stress intensity force VzPR, as used in the equation of moments in the paragraph above,

' Y is derived as follows, in accordance with thin sphere theory: Assuming a .1 inch circle at any point on the shell of a thin sphere, the stress intensity in a tangential direction around the 1 inch circle in pounds per inch of periphery may Assuming a comparatively large sphere radius R, so that the cosine of a central angle half the size of this 1 inch circle on the shell will be substantially unity, the radially inward component of the total tangential stress on the periphery of the 1 inch circle will equal the totaltangential stress x the radial projection, at the center of the 1 inch circle, of a line tangent to the radius at the edge of the circle and representing the total tangential stress Still considering this 1 inch circle, and assuming the cosine of the central angle to be unity, the radially inward component will be x the total tangential stress,.

The radially inward component is thus Since the radially inward component of the total tangential stress on the circle and the total pressure outward against the circle must be equal, they may be equated. Therefore 1S 1rP 2 E '4 Solving this for S, we have s: VzPR.

While we have shown and described 'certain embodiments of our invention, it is to be understood that it is capable of many modifications. Changes therefore in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims, in which it is our intention to claim the novelty inherent in our invention as broadly as permissible in view of the prior art.

What we claim as new and desire to secure by Letters Patent is:

1. A pressure tank, including; a shell having a head-ring welded thereto; a groove in the outward face of said head-ring; a gasket in said groove; a door-ring adapted to be drawn into enga'gement with said gasket; an outwardly spherically curved head-plate of relatively thin metal said head-plate having a thinness relative to its diameter such that it deforms under the action of pressures normally maintained within the tank when in use, said head-plate being substantially less than a hemisphere and welded to the inner face of said door-ring, so that any tendenvy of the door-ring to tilt due to the action upon it of the spherical head-plate when under pressure is minimized and leakage at the gasket is thereby prevented at a point intermediate between the cross-sectional center of gravity of said door-ring and the outer'extremity of said ring, whereby the tension developed when the head is under pressure substantially neutralizes the rotational moments caused by the tension in the bolt and the pressure against the inner face of the ring; lugs on said door-ring; bolt-members on said head-ring; and bolts whereby said doorring is drawn into engagement with said gasket andhead-ring.

'2. A pressure tank, including; a cylindrical the cross-sectional center of gravity of said doora shell having a head-ring welded thereto; a doorring adapted to engage said head-ring; a gasket between said head-ring and'said door ring; lugs on said door-ring; bolt members on said headring; bolts whereby said door-ring, gasket, and,

head-ring may be drawn into engagement; and an outwardly spherically curved head-plate of relatively thin metal, said head-plate having a thinness relative to its diameter such that it deforms under the action of pressures normally maintained within the tank when in use, said head-plate being welded to the inner face of said door-ring at a vertically'outward distance from the cross-sectional center of gravity of said door-ring substantially satisfying the equation where e is the distance from the center of gravity to the axis of. the bolt, R is-the spherical radius .a of the head-plate, and r is the radiusof the door ring, all distances being in inches, so that any tendency of the door-ring to tilt due to the action upon it of the spherical head-plate when under I pressure is minimized and leakage at thegasket is thereby prevented.

3. A pressure tank, including; a cylindrical shell having a head-ring welded thereto; a doorring adapted to engage said head-ring; a gasket between said head-ring and said door-ring; lugs on said door-ring; bolt members on said headring; bolts whereby said door-ring, gasket, and head-ring may be drawn into engagement, and an outwardly spherically curved head-plate of relatively thin metal, said head-plate having a thinness relative to its diameter such that it deforms under the action of pressures normally maintained within the tank when in use, said head-plate being welded to the inner face'oi said door-ring at a vertically outward distance from rlng to tilt due to the action upon it of the spherical head-plate when under pressure is minimized and leakage at the gasket is thereby prel vented.

4. Apparatus of the character described, in-

eluding; a cylindrical shell having a head ring; a door ring adapted to engage said head ring; a gasket between said head ring and said door ring: means for drawing said door ring, gasket, and head ring together; and an outwardly spherically curved head-plate of relatively thin metal, said head-plate having a thinness relative to its diameter such that it'deforms under the action of pressures normallymaintained within the tank when in use, saidhead-plate being substantially less than a hemisphere and connected to said door ring at a'point intermediate between the cross sectional center of gravity of said ring and an outward extremity of said ring, so that any tendency of the door ring to tilt due to the action upon it of the spherical head-plate when under pressure is minimized and leakage at the gasket is.

thereby prevented.

5. Apparatus of the character claimed in claim 4, wherein the means for drawing said rings and gasket together are radial lug members adapted to receive bolts.

. ROBERT A. DAVIS.

JOHN F. I I ultim- 

